TlIK MAKYLAM) CVCADS. 41o 



possible exceptions tlie trunks appear to iuive Ijeen tlerived from more or 

 less arenaceous deposits, referable either to this or to the Patapsco forma- 

 tion. There is no veiy dcfhiitc cxidcnce that the Arundel, which is a 

 hitrhly argillaceous terrane. has yielded anw unless, possibly, bv secondary 

 deposition from the Patuxent formation. .Most of the veg;etal)le tissues 

 eml)edded in the Arundel are either carbonized oi- replaced by iron,silicifica- 

 tion at times occurring near its contacts with the more arenaceous Patux- 

 ent and Patapsco terranesoi- well to the laiidwai'd, where its deposits tend 

 to be somewhat arcMuiceous within the formation itself. Xear the Patapsco 

 contact, for example, a coniferous trunk partly lignitized and partlv 

 silicified was found, and a silicified coniferous trunk was excavated from 

 an Arundel sand lens near Brookland. The circmnstance that lignitized 

 cycad trunks have never been reported bv the Anmdel u"on miners should 

 not. however, carry much weight, since if occurring they would doubtless 

 be compressed or otherwise distorted and therefore much less readily 

 recognized. Besides, unless the trunks occurred more commonly than in 

 the Patuxent and Patapsco formations, the chances of their being encoun- 

 tered at all by the iron miners would be very slight, for no one has ever been 

 known to exhume a silicified cycad trunk from the perhaps equally numer- 

 ous Patapsco and Patuxent excavations for sands and gravel. One must 

 not infer, therefore, that the cycadaceous element of the vegetation of 

 Arundel times was necessarily less prominent than that of the Patuxent 

 and Patapsco epochs. The fact that there was such an element in the 

 Arundel flora is shown by the occurrence of frond impressions in its clays 

 and iron ores. The conditions for the entombing of the trunks may at 

 that time have l^een less favorable, as the conditions of permanent presei- 

 vation in such a form as to favor detection certainly were. 



There is no verj- definite evidence that any of the trunks have been 

 derived from the Raritan terrane, though several may well have been. 

 The most probable case is that of the trunk, W. C, B., No. 6346, found 

 north of Woodwardville, but the point at which that trunk was found is 

 not positively known. Moreovei-, its much worn condition suggests 

 redeposition in the Pleistocene. 



That the original beds of the trunks were certainly largely arenaceous 

 instead of argillaceous is proved by their silicification, hereinafter men- 

 tioned, though semisilicified conifei'ous wood is occasionally found in 

 slightly sandy clays. 



